In conventional public land mobile networks, the setting of mobility parameters are based on the serving frequency and/or on probably or typically available target frequencies, which is often only a rough estimation of the used settings; thus the used settings are often not optimal in a typical user situation.
The mobility in cellular radio networks is based on periodic measurements (of the radio environment by the user equipments), exploring the surrounding area, i.e. neighbour cells, of a given (serving) cell to identify if better radio conditions can be provided, by another cell, to the user equipment. In a continuous network layer this is typically given within a given frequency range. In this layer, the measurements must be triggered with a higher periodicity when the signal strength or quality of the cell falls under a certain limit to ensure early identification of a target neighbour cell and to ensure a reliable handover to this target cell.
The situation is more complex if other frequency layers of the same RAT (Radio Access Technology) or even other RATs come into consideration for mobility and must be considered by the terminal for neighbour cell measurements.
These measurements are typically more complex because the terminal needs to change the serving frequency (or frequency range) and has to perform a synchronisation to the cells on the other frequency layer (of the same RAT) or on the other RAT.
Network planning activities have the strong tendency to try to configure the network (or network components) in a generic way, i.e. as much as possible without a location specific planning. In the field of mobility, ANR (Automatic Neighbour Relationship), a 3GPP standardised functionality, gives the opportunity to avoid planning neighbour relationships but with the drawback that the terminals (or user equipments) are requested to perform periodic measurements and are configured in a generic way as well. So for all cells, the measurements are periodically triggered to explore intra-frequency, inter-frequency and inter-RAT relationships towards neighbour cells. Even when the neighbour cells are found and configured, the measurements are triggered periodically, at least in case that a certain signal strength or quality threshold is reached in the serving cell.
For intra-frequency relationships, to ensure mobility within a given layer, i.e. within the same radio access technology, such a generic pattern of periodic measurements might be sufficient, but involves drawbacks in other scenarios, such as:
triggering of inter-frequency measurements even if the centre frequency of the respective specific band is not available in the area of a considered (serving) cell and/or
triggering of inter-frequency measurements even if the mobility of the user equipment can perfectly be covered by the (neighbouring) cells having the same frequency (or the same frequency band) as the given (serving) cell, and/or
triggering of inter-RAT measurements even if the mobility of the user equipment can perfectly be covered by the (neighbouring) cells having the same radio access technology as the given (serving) cell.
Generally, unnecessary measurements—especially inter-frequency and inter-RAT measurements—reduce the throughput from a customer (or subscriber) point of view because transmission gaps during data transfer are required to perform these measurements of another frequency or RAT (with respect to the serving frequency or serving RAT). Additionally, from network point of view unnecessary measurements reduce the statistical reliability of the remaining measurements in the configured measurement gap, if the trigger conditions of the serving cell are reached for these measurements.